In a single-wafer rapid thermal processing reactor (RTP), one of the critical process parameters is the temperature of the wafer. Infrared pyrometers have been used to measure the temperature of a wafer being processed in the rapid thermal processing reactor. The reactor typically uses several heating lamps arranged in some predetermined pattern and situated on one side of the wafer. A disc of quartz functioning as a quartz window separates the heating lamps from the wafer being processed in the reactor. The quartz window therefore maintains chamber vacuum and also transfers the radiant heat from the heating lamps to the wafer. The pyrometer is typically mounted remotely from the wafer and on the same side of the quartz window as the heating lamps. The wafer temperature detected by the pyrometer is then advantageously used to control the intensity of the heating lamps in order to increase or decrease wafer temperature depending on predetermined processing parameters or recipes.
Since the quartz window is situated between the pyrometer and the wafer, the pyrometer must, in effect, detect the radiant light emitted from the heated wafer through the window. Given the intense heat that the quartz window is subjected to, originating from both the heating lamps as well as the wafer itself, the temperature of the window may reach significant levels. The intense temperature of the quartz window may cause inaccuracies in the detected wafer temperature, which may adversely alter actual wafer processing parameters.